Effective Conductivity of a Cloudy Ionosphere - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 296

300

250

200

150

100

50

0

0 2 4 6 8 10 12 14 16

j an / j ∞

Fig. 10.2. Height dependency of the ratio of anomalous j an current to the back-
ground undisturbed current j ∞

where I 1 is the current far from the inhomogeneity,
c = ρ 1 − δ 2 ) 2 g − 1 , ρ 2 − δ 2 ) g − 1 ,

( δ 1 − b =2 ρ 1 ( δ 1 −

j 1 = E 0 σ P 1 + σ 2 H 1 ,

1 , 2 = σ H 1 , 2 h − 1 1 , 2 = σ P 1 , 2 h − 1

1 , 2 , 1 , 2 ,

g =( ρ 1 + ρ 2 ) 2 +( δ 1 − δ 2 ) 2 , 1 , 2 = σ 2 H 1 , 2 + σ P 1 , 2 .

Here σ P,H is the Pedersen or Hall specific conductivities outside the inhomo-
geneity (index '1') or of the inhomogeneity itself (index '2'). The x -component
of the current is
j x = j P 1 + a 0

r 2 j P 1 ( ρ 1 −

δ 2 ) g − 1 , ρ 2 )+2 j H 1 ρ 1 ( δ 1 −

(10.3)

where j P 1 = σ P 1 E 0 is the Pedersen current far from the inhomogeneity. The
second term in (10.3) is a component defined by the inhomogeneity, it consists
of two parts. The first one, proportional to ( ρ 1 − ρ 2 ) , is the anomalous Ped-

ersen current and the second one is the term defined by the Hall conductivity
anomaly.
Figure 10.2 shows the ratio of anomalous current j an = j x −

j P 1 to the
background undisturbed current j P 1 as a function of ionospheric height. The
local electron concentration perturbation is 10%. A conductivity change of
10% results in a 10-20% anomalous current on the bottom of the D-layer
( h = 60-70 km). At altitudes 70-100 km, the anomalous Pedersen current is
5-10 times greater than the background current due to increasing β e and a
small β i . Here σ P is defined by electrons alone, σ P ≈ σ Pe . One can see that

a small conductivity perturbation significantly affects the Pedersen current.